This proposal is a request for continued partial funding of the Flow Cytometry Core Facility (FCCF) within the Multipurpose Arthritis Center (MAC). The primary purpose of the FCCF is to make available to MAC investigators access to the equipment, trained personnel and expertise to perform cell analysis and purification with state-of-the art equipment and techniques on a reasonable cost for services basis. The facility employs a dedicated full-time and experienced cytometer operator who serves over 100 individuals per year. At the present time the FCCF contains a FACScan five parameter single laser analytical cytometer and a FACStar plus six parameter, dual laser cytometer/sorter. The computers which control these instruments have been networked for efficiency, and a variety of programs for univariate through tetravariate fluorescence analysis, DNA curve fitting, immune monitoring and numerous other applications are available. Sufficient funds are requested to ensure stable salary support and continuing education for the operator, and to cover a portion of the field service contracts for the cytometers. The requested level of support will be sufficient to cover approximately 50% of the actual cost of operating the FCCf and it is estimated that this will allow the present rate of $50/hour for MAC investigators to be sustained into the foreseeable future.